The non-volatile storage of data or states is often necessary in integrated semiconductor circuits. Non-volatile memories are suitable in particular for holding small to medium volumes of data, such as, by way of example, redundancy data, data keys and self-test results. These can thus be repeatedly made available to the user.
A number of non-volatile memory elements are known to the person skilled in the art. As an example thereof, mention shall be made of the textbook “Mikroelektronische Speicher” [“Microelectronic Memories”] by Dietrich Rhein and Heinz Freitag, ISBN 3 211 82354 3, in particular pages 105 to 108 and pages 122 to 127. Non-volatile memories include electrically programmable read-only memories or EPROMs, and flash memories with floating gate technologies. Ferroelectric and magnetic read/write memories are also known. These memories have the disadvantage in common that complicated process steps are needed during their fabrication, which lead to higher product costs.
Another form of non-volatile memories uses severable interconnects in the integrated semiconductor circuit, so-called “fuses”. Writing to such memories requires separate devices such as, by way of example, laser cutters or means for generating high currents. It is thus not always possible for the users of such memories themselves to write to the memory. This may be a disadvantage particularly when such memories are used in mobile systems.
What is more, severable fuses entail the risk of separated connections at least partly growing together again during operation. As a result, data stored in the memory may be corrupted without this being perceptible to the user.